Chemists at the University of Illinois have determined that temperatures inside gas bubbles collapsing in a liquid reach roughly 20,000 degrees Kelvin—four times hotter than the surface of the Sun. They made the discovery by blasting the liquid with intense sound waves and measuring "sonoluminescence," the light emitted from the bubbles as they form and collapse. According to the researchers, it is the first time anyone has measured the temperature inside a single collapsing bubble.

Their work was supported by the National Science Foundation and the Defense Advanced Research Projects Agency, and published in the March 3, 2005, issue of the journal Nature.

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2015, its budget is $7.3 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 48,000 competitive proposals for funding, and makes about 11,000 new funding awards. NSF also awards about $626 million in professional and service contracts yearly.